Asian Journal of Chemistry; Vol. 26, No. 7 (2014), 1995-1997
ASIAN JOURNAL OF CHEMISTRY
Synthesis of Glyoxalic Acid Using Methyl Dichloroacetate by Microwave Method
*
QIAN NIU, XIONG LUO, SHOU-GAO LI, YING MENG and FU-XIANG LI
Research Institute of Special Chemicals, Taiyuan University of Technology, Taiyuan 030024, Shanxi Province, P.R. China
*Corresponding author: Fax: +86 351 6111178; Tel: +86 351 6010550-3; E-mail: L63f64x@163.com; rencizhe@126.com
Received: 10 April 2013;
Accepted: 17 June 2013;
Published online: 22 March 2014;
AJC-14945
Microwave irradiation was used to synthesize glyoxalic acid from methyl dichloroacetate. The effects of the irradiation time, reaction
temperature, reactant ratio and different alkali on the yield of glyoxalic acid were studied and also compared with those effects under
conventional heating. The yield of glyoxalic acid can reach 84.6 % within 6 h under the microwave irradiation, which is 12.2 % higher
than that under conventional heating within 12 h. The optimum reaction time is 7.5 h and the optimum reaction temperature is 75 °C under
the microwave irradiation. The results indicated that microwave irradiation was superior to the conventional heating obviously.
Keywords: Microwave irradiation, Methyl dichloroacetate, Synthesis, Glyoxalic acid.
time in organic synthesis. The microwave irradiation method
has been applied to many kinds of reactions in organic synthesis
and is becoming one of the hot point for green chemical reaction
lately.
INTRODUCTION
Glyoxalic acid, the most simple keto acid, has properties
of both acids and aldehyde, which could be found in some
animal's body fluids and unripened fruits. As an important
organic synthesis intermediate, glyoxalic acid can be widely
applied in fine chemicals synthesis, such as varnish, medicine,
dyestuff, spicery, plastics additives and industrial chemicals.
It can also be used in the production of oral penicillin, vanillin
and allantoin, etc1.
The yield of glyoxalic acid from the hydrolysis reaction
of methyl dichloroacetate under conventional heating method8
is only 70 %. We have reported a novel microwave heating
technique as an alternative to the conventional heating in
synthesis of glyoxalic acid. This paper aims to explore the
speed and degree of reaction under the condition of microwave
and to find the optimal reaction conditions for the synthesis of
glyoxalic acid, to provide application foundation and technical
support for comprehensive utilization of methyl dichloro acetate.
The reaction equations are described as follows:
Several techniques have been reported to produce
glyoxalic acid including, oxidation of glyoxal2,3, ozonation of
maleic acid4, hydrolysis oxidation of dichloroacetic acid5 and
oxalic acid electrochemical reduction6,7. But all these methods
have many disadvantages such as huge facilities, large invest-
ments, complex mechanical works and potential environmental
pollutions, high costs for operating and maintaining. Thus,
the methods mentioned above are not satisfying in practical
application, it is urgent to seek a reasonable and economic
method.
NaOH
Cl2CHCOOCH3 + H3COH
→
(H3CO)2CHCOONa + NaCl
(H3CO)2CHCOONa + H2SO4 OCHCOOH + Na SO
→
2
4
EXPERIMENTAL
Methyl dichloroacetate is a by-product when producing
methyl chloroacetate by using methanol esterify mother liquor
of chloroacetic acid (contains 30-35 % dichloroacetic acid).
The synthesis process of the glyoxalic acid using the methyl
dichloroacetate as the raw material has the characteristics of
simple process, low costs and good product quality. At the
same time it also takes advantage of the mother liquor of
chloroacetic acid and reduces emissions to the environment.
As a new heating technology, the microwave extraordi-
narily improves the efficiency and yields and shortens reaction
Ethyl dichloroacetate (Industry grade, purity 99.9 %), w
(sulfuric acid) = 98 %, sodium hydroxide (AR, 96.0 %),
potassium hydroxide (AR, 85.0 %), sodium carbonate (AR,
99.8%), sodium bicarbonate (AR, 99.5 %), sodium acetate
(AR, 99.0 %), potassium carbonate (AR, 99.0 %) and methanol
(AR, 99.5 %). Microwave chemistry reactor (Gongyi City
Yuhua Instrument CO., LTD) with microwave frequency 2450
MHz, power 80-800 W.
Synthesis of glyoxalic acid: In a 100 mL, three-necked,
round-bottomed flask a certain quantity of methanol should